NEW YORK | This road trip — three games against the defending AL champions and three against the league’s resident bullies — wasn’t supposed to end like this. Not when it started, and a 2-4 record would have been considered a success, and not when the Washington Nationals were blowing leads and dropping pop-ups in Tampa while their manager’s job status was rumored to be on an hour-by-hour basis.

The idea of the Washington Nationals taking two out of three at Yankee Stadium, thoroughly controlling a game delayed by 5 1/2 hours to the point that Yankees fans turned vitriolic on their own team, was preposterous.

And yet, it happened on Thursday with a 3-0 victory, giving the team almost assuredly the most improbable series win it will have this season.

In four short days, the Nationals went from getting swept by the Tampa Bay Rays to beating the Yankees twice in a series they could have swept if not for a late New York comeback on Tuesday. The questions about manager Manny Acta’s job status had, at least momentarily, faded.

The victory gave the Nationals just their eighth win on the road this season and their third series win of the season. Even more shocking was the ease with which it came Thursday, with rookie right-hander Craig Stammen shutting the Yankees out for 6 1/3 innings and earning his first big league win thanks to two bugaboos-turned-bulwarks – the Nationals’ bullpen and defense.

After Adam Dunn’s RBI double in the first, Stammen contentedly threw strikes against an aggressive Yankees lineup that came out swinging after spending all day stewing, willing to let his defense make plays behind him.

That was something of a leap of faith given the Nationals’ NL-leading 61 errors. But an outfield of Willie Harris, Corey Patterson and Austin Kearns is about the best configuration manager Manny Acta will be able to give a pitcher this year. And for a second straight night, the Nationals’ fielding was clean, even impressive at points.

Ryan Zimmerman made a diving stop in the fourth and forced out Mark Teixeira at second to end the inning. Anderson Hernandez ranged deep into the hole behind second to deny Johnny Damon a broken-bat single in the sixth. And there were two plays that probably saved runs.

In the fifth, Kearns fielded a single from Nick Swisher and made a sharp throw to Cristian Guzman at second to throw out Swisher as he stretched for a double. When Hideki Matsui singled on the next at-bat, there was no runner on second.

Harris’ catch in the seventh had the same effect. Alex Rodriguez led off the inning with a searing liner that tracked right over Harris’ head in left. He initially turned the wrong way, but recovered in time to make a diving catch, sliding near the warning track.

The next two batters, Robinson Cano and Swisher, singled and doubled. And again, no runs scored. Harris’ catch saved a run at the start of the inning, and Guzman’s play at the end of it might have saved two.

Ron Villone relieved Stammen, walking pinch hitter Jorge Posada with two outs. Then Derek Jeter, kept out the last two days with a stiff left ankle, bounded up the top step of the dugout to pinch hit for Ramiro Pena, sending the hardy remainder of the 45,143 paying fans into a frenzy.

The Nationals replaced Villone with Julian Tavarez, who worked Jeter to a 1-2 count. He threw one more sinker, and the future Hall of Famer punched it up the middle. Guzman made a sliding stop, flipping to Hernandez at second and stealing the moment from the man who seems to command them innately in the Bronx.

On offense, Wil Nieves’ bases-loaded walk in the fourth and Ryan Zimmerman’s double in the fifth pushed across a pair of runs.

Joe Beimel allowed only a walk in the eighth, and after Cano singled to start the ninth, Mike MacDougal induced a double play. He earned his second save in as many days — and second since 2006 — when Harris made a slick running catch to end the game.

Stammen had his first win, Acta had momentary vindication and the Nationals had a series win that will be hard to top this year.